If you are an agnostic or a nihilist, it is already difficult to answer any ethical question from a perspective of non-commitment to any philosophy. I mean how can you know if anything is shameful if you believe no truth can be ascertained which is the point of nihilism?
Then you are left with the measures of public opinion or scientific opinion on values. But public opinion even though indispensable in actual life, you can still reckon as a thinker, is not a reliable measure of truth, but you also find yourself in the contradictory situation of not believing in any substantial truth anyway except perhaps that of the mundane life. So I reckon you'll end up conforming to the public opinion or order of the day as a matter of convenience while knowing deep inside it is philosophically arbitrary.
Then you may consult science as a firmer ground for what is right. But then you've learned science mostly concerns tangible things about human life such as physical health not shame or honor, but you'll still find scientists taking pride in their achievements or feeling shame if found wrong or caught plagiarizing stuff.
So you find confirmation that values are indispensable in life but don't find a reliable means of grounding them except in the naturalistic science but you may also find natural science's notions of good and bad and honorable and shameful very narrow.
You may then start to see why in our modern "demystified" world, many world intellectuals turn to reading/writing novels/fiction to find comfort and why the entertainment industry has grown into insane proportions. I mean, the conclusion seems inescapable that some "crazy stuff" has to be out there for us to sustain life. However, religion has a feature of seriousness to its "crazy" claims and a claim of response to man's yearning for "higher" ends, but modern entertainment doesn't pretend that it is anything other than just that: entertainment.
Well, as a peculiar kind of theist, I know there's no easy way out of nihilism for a nihilist or for our nihilistic world for that matter. But I have found a few weeks of diving into the NDEs stories and studies far more productive, emotionally gratifying and intellectually promising, provided that you are not already held back by the belief that "those are hallucinations made by the brain" before having acquainted yourself with them adequately. Engaging some Romantic literature may also help you appreciate a meaningful way of experiencing reality. But I hope these proposals aren't off-topic.
In sum, nihilism is an insecure and contradictory intellectual (non)position leading to emotional insecurity and questionable moral life. You have to find a way out. I only hope my answer didn't come off as judgemental or condescending. Peace!